Transport mechanisms of the type with which the present invention is concerned are used, for example, in automated money machines at I.D. (identification) check points. The identification cards may carry visible or invisible information symbols. The purpose of the transport mechanism is to accept the card when it is inserted at the entrance to the reader; it then moves the card past an evaluation device where the symbols are interpreted in order to determine whether or not the current holder is authorized to undertake a certain business transaction, e.g. remove money from a bank account. After the card is read, the mechanism may eject the card at an exit point which is separate from the entrance. Another possibility is to reverse the direction of transport when the card reaches a certain point within the mechanism (the reversal point). The card is then ejected through the inlet. The system which reads the cards operates on magnetic, electrostatic, or optical principles depending on how the information is stored on the card. When a card is to be identified and read, it must be moved at a uniform velocity and at the correct distance relative to the evaluation device in order to avoid mistakes in the evaluation.
Card-shaped recording media are usually made out of a plastic which is elastic yet resists bending. Nonetheless, these cards can get bent out of shape depending on how often they are used, how they are stored, and how old they are. If a bent card is transported past an evaluation device, the distance between it and the reader tends to vary because of the deformation of the card. Therefore, it is necessary to provide a transport mechanism which will accept deformed cards and convey them correctly past the evaluation device. The mechanisms which have been designed in the past are equipped with many costly and inefficient rollers, at least in the region around the evaluation device. The rollers usually push on both sides of the card. However, these roller-operated devices cannot adequately transport the card-shaped recording medium because the distance between the roller pairs relative to the overall length of the card is too large. Furthermore, these mechanisms are only conditionally able to transport a card past the evaluation device at a constant velocity since there are velocity peaks induced whenever a card is initially grabbed by a pair of rollers and whenever it leaves the influence of a roller pair. In addition, these kinds of devices tend to experience breakdowns which might be caused by a bent card wrapping itself around a roller, for example. Another problem arises when the force applied by a single pair of rollers is not sufficient to accelerate the recording medium as fast as desired. This problem leads back to the fact that the surface area which presses on the card is very small, this small surface area promotes particularly fast wear and smoothing of the roller, causing the force available to accelerate the card to decrease yet further. Roller readers have the additional disadvantage that the roller mechanism is costly to manufacture.
As is apparent from the foregoing, all of the problems associated with a roller reader are caused by using rollers as the only transport elements.